1. Field of the Invention
The present invention relates to a side support device in the seat back of an automotive seat.
2. Description of Prior Art
In conventional side support device provided in the seat back of automotive seat, several transmission systems, including a threaded lead screw and threaded nut system, link members and shafts, are arranged in the seat back frame so as to transmit and transform the rotational drive force of an electric motor into the inward and outward swinging motion of both side support frames upon the respective lateral frame sections of seat back frame. Namely, the two side support frames are rotatably supported on those respective lateral frame sections of seat back frame, such that both side support frames are simultaneously rotatable about their respective lateral frame sections of seat back frame in the direction inwardly and outwardly of the seat back frame in order to permit adjustment of side support force to both sides of an occupant sitting on the seat. In this side support framework, some transmission systmes mentioned above and relevant mechanic elements are conventionally disposed in a manner projecting inwardly of those two side support frames. This is known, for example, from the Japanese Utility Model Laid-Open Pubs. Nos. 60-97634 and 2-143061, which show the transmission systems (gears, motor support brackets, shafts, threaded lead screw, threaded nut in mesh with the threaded lead screw, etc.) to be disposed inwardly of the seat back frame in a manner projecting forwardly of same seat back frame. Incidentally, a foam padding, which covers those side support frames, seat back frame and transmission systems, is normally of a thin thickness as compared with the thickness of foam padding used on the seat cushion frame. Such seat back structures with side support device has been found defective in that the tramission systems and associated mechanic elements noted above are felt hard by the back of an occupant sitting on the seat, and thus, the occupant may not enjoy a comfortable support touch on the seat back.